Neurofibromatosis type 1 (NF1) is the most common hereditary disease predisposing to neoplasia. It affects approximately 1 in 3500 individuals with all races and both sexes affected equally. The gene for this dominant disease has recently been isolated and the sequence of its cDNA determined, yet the function of its product is unknown. Preliminary evidence suggests that the NF1 gene has role in the regulation of cell proliferation. This project addresses the function of the NF1 gene product by exploiting our large collection of NF1 tissues and the DNA sequence information derived from the recent isolation of the NF1 gene. Their growing collection of NF1 tissues includes samples from 143 patients received fresh and 150 additional archival samples. DNA will be analyzed from nontumor tissues and from benign and malignant tumors from NF1 individuals. Amplification of each of the NF1 exons by the polymerase chain reaction followed by analysis for single strand conformation polymorphisms (SSCPs) will detect point mutations, deletions, and insertions as fragments of altered mobility in electrophoretic gels. The DNA sequence will be determined for any abnormal fragment thus identified to delineate specific mutations. The type and location of mutations will be correlated with clinical features of this disease in order to delineate functional regions of the NF1 gene. Tumors of the types found in NF1 from individuals who do not have NF1 will be similarly analyzed to determine whether mutations at the NF1 gene play a role in those tumors. To determine the effect of the mutations on NF1 gene expression, RNA will be analyzed. The type and location of mutations will have predictable effects on NF1 gene expression such as reduced RNA levels or transcripts with altered size due to mutations at splice sites. These effects will be investigated by analysis of NF1 transcripts from cells containing mutations. The role of genomic imprinting in the occurrence of spontaneous cases of NF1 will be examined by following restriction fragment length polymorphisms in families with new mutations. The role of the tumor suppressor p53 in NF1 tumors will be investigated by analyzing NF1 tumor DNA for SSCPs. This study will provide an understanding of the biological function of the NF1 gene product in normal and abnormal cells and permit better prognostic testing of affected individuals in order to determine the likely course of their disease and possibly determine the appropriate therapy.